Script versus short story
One of Christie's shortest short stories, this had to be embellished quite a lot to work as a 50-minute adaptation. Luckily, Renwick's additions make sense and enhance the story, to some extent. Personally, at least, I've always found it somewhat unbelievable that Poirot would just happen to be passing the chemist's in Barchester, just happen to notice Langton's name (a man he had met once at a dinner party), and then just happen to make the connection that it would have something to do with Harrison and his wife by bumping into Langton in the street. Renwick makes the sensible decision to include a garden fete, which Poirot, Hastings and Japp attend on Hastings's suggestion (of course, it would take Hastings (or Ariadne Oliver, in his later years) for Poirot to attend something like that). At the garden fete, they meet Harrison and Molly Deane, and Hastings takes photos of Langton, Harrison and Deane (his new hobby). Harrison becomes a long-time friend of Poirot here, or rather, Poirot was a friend of his father, who was one of his first friends in England. Poirot, for fun it seems, reads the tea leaves of Molly Deane and notices the bright red lipstick on the cup (belonging to Langton, who is cleverly dressed up as a clown on the fete). Later, Poirot gets stung by one of the wasps in Harrison's garden and has to go to the local chemist (where he discovers Langdon's name in the poison registry). Moreover, Japp (who is added to the story) is admitted to hospital with appendicitis, in an amusing subplot that leads to Japp identifying the doctor of Harrison. Miss Lemon is added, and she regularly attends fitness classes in the same street that Harrison visits his doctor (providing Poirot with yet another link). Also, Molly Deane becomes a fashion model in the adaptation, thus allowing for an extravagant fashion show that also provides a clue to the crime (it turns out Langton has a photo of Deane in a new season's dress; proof of their affair). Another clue added to the mix is a large amount of petrol in the water tank outside Harrison's house (Poirot notices the smell), proof that Harrison substituted the petrol with water to ensure that Langton wouldn't succeed with the wasp killing and would resort to cyanide. Finally, Poirot is seen breaking into Langton's house (!) to remove the cyanide and replace it with washing soda, so that Harrison wouldn't succeed (which is much more believable than just placing some soda in his jacket pocket). In the end, then, the adaptation adds a long list of clues which Poirot has to piece together. Consequently, this becomes an quintessential Poirot episode, since he arrives at the right conclusion through his excellent observational skills and his knowledge of human psychology. The episode is also one of the darker ones of the series up to this point.
Directing, production design, locations, soundtrack
Farnham's direction is well executed. He displays the all-important wasps' nest from all possible angles, and nicely displays the London suburb summer, as well as the fashion show. Locationwise, a house near Shepperton becomes Harrison's house, Arnos Grove station becomes 'Marble Hill Station', an Art Deco house in Surrey (seen briefly in The Veiled Lady) becomes Langton's house, and Japp ends up at the Royal Masonic Hospital in Ravenscroft Park. See this website for location photos. The soundtrack is great for this one, and 'The Height of Fashion' (Molly Deane's theme) is available on the latest CD.
Actors and characters
By this point in the series I really feel that Suchet's Poirot has settled. By now, Poirot looks and sounds exactly the same as in the most recent episodes. It's a testament to Suchet's skill, that so little has changed. As he tends to note when interviewed about the series, Poirot never really changed in Christie's descriptions, and neither should his portrayal of him. Of the guest actors, the standouts are Martin Turner as John Harrison and a young Peter Capaldi as Claude Langton, but the entire cast works well for this episode.